This invention relates to the partial oxidation of metals-containing hydrocarbonaceous fuels for the production of synthesis gas, fuel gas, or reducing gas. More specifically, it relates to the noncatalytic partial oxidation of liquid hydrocarbonaceous fuels with total recycle of the unconverted particulate carbon and without build-up in the system of the metals normally present in the fresh hydrocarbonaceous fuel feedstock.
Hydrocarbonaceous fuels, such as crude oil contain inorganic and organic compounds of iron, nickel and vanadium. During the partial oxidation reaction, unless prevented these compounds could react with the refractory lining of the reaction zone in the gas generator. However, by removing the metals such reactions are prevented. Thus, the generator is operated so that a portion of the carbon in the fuel passes through the reaction zone as unconverted particulate carbon. This particulate carbon sequesters the metals and leaves the reaction zone as soot entrained in the raw effluent gas stream. The unconverted particulate carbon with the associated metals and metal compounds is recovered and may be recycled to the gas generator as a portion of the reactant fuel feed. While this improves fuel efficiency, the metals in the system may also build up and under certain conditions contribute to problems downstream in the system such as by forming deposits in heat exchangers and other equipment that may plug passages and/or foul tubes.
By the subject process, there is a reduction of about 50 wt.% of the metals and metal compounds that are recycled to the gas generator. This may extend the life of the equipment, increase the efficiency of the process, and yield valuable by-product materials rich in nickel and vanadium.
Entrained particulate carbon may be removed from the raw effluent gas by quenching and scrubbing with water such as described in coassigned U.S. Pat. Nos. 3,069,251 and 3,232,728. Recovery of the particulate carbon from carbon-water dispersions by the steps of adding a light oil to the carbon-water dispersion, separating water and light oil-carbon dispersion in a decanter, mixing the light oil-carbon dispersion with heavy oil and heating in a preheater, and vaporizing the light oil in a flash drum or distillation tower is described respectively in coassigned U.S. Pat. Nos. 2,999,741; 2,992,906; 3,044,179; and 4,134,740. Typical decanting procedures are described in coassigned U.S. Pat. Nos. 3,980,592 and 4,014,786.
The carbon-recovery zone in prior-art systems was operated in such a manner that a large amount of the ash in the mixture of soot-water dispersion and liquid organic extractant entering the decanter was transferred along with the soot to the liquid organic extractant layer that separates out in the decanter along with a separate water layer. However, with total soot recycle excessive metals build-up in the system may occur. Further, nickel and iron carbonyls may form from the suspended metals in the grey water. Under certain conditions such metal carbonyls may decompose or form insoluble compounds that might foul surfaces or plug equipment.
In contrast, by the subject process which includes recycling about 80-100 wt.% of the particulate carbon and soot produced, a significantly large portion of the ash in the soot-water feedstream entering the decanter is transferred to the grey water layer that separates out in the decanter and may be thereby easily removed from the system. By this means, the aforesaid problems are substantially reduced or eliminated.